The first official coin to commemorate a royal engagement is to be created to mark the betrothal of Prince William to Kate Middleton.

The Royal Mint will produce the £5 collector's piece in the coming months and have it on sale before next year's wedding.

The engagement, which has caught media attention around the world, is also likely to be celebrated by a new stamp.

The Royal Mail said the aim of its special stamp programme was always to honour important events in the country's heritage and it would be consulting with the Queen and other parties before anything was produced.